1. Field of the Invention
This invention relates to an improved plastic sheet which can be used as an insulating lining between a foundation and facing materials such as ceramic tiles. More particularly, this invention relates to a plastic sheet which can compensate for different rates of thermal expansion between the underlying foundation and the external facing.
2. Description of the Prior Art
Installing external or internal building facing materials in the form of ceramic tile surfacing or plaster presents many problems. Because of the different expansion stresses within the wall or base foundations and the covering, damage often results in the form of cracks or peeling of the facing from the inside out. Moisture penetration through the facing can also induce damage when, for example, plasterboard or sheetrock is used as the underlying foundation. Ceramic tiles are frequently laid in the so-called "thin layer" process which utilizes a suitable contact adhesive. In practice, it is difficult to find suitable adhesives which are equally suited to the underlying foundation as well as the back of a ceramic tile. The materials requiring bonding are, in practice, so varied, that the choice of adhesive always involves a compromise.
Patent CH-PS 630 984 discloses a moisture-impermeable plastic sheet which serves as an insulating lining for building surfaces. This sheet has a parallel, alternating, open, sectioning, which is dovetail-shaped in cross section. Since this plastic sheet is expandable in a direction transverse to the sectioning, it enables longitudinal compensation in effecting latitudinal adjustment at the foundation. The known plastic sheet, with its webbing on the one side, forms anchoring ribs which are preferably inserted in the hardenable underlying foundation material and function as anchors. The dovetail-shaped grooves formed in this manner form openings facing outwardly which function to satisfy aesthetic requirements and to drain off moisture in a vertical direction when they are mounted vertically.
A plastic sheet of this kind, as a rule, will only adequately lend itself to mounting on a wall in a mortar or adhesive medium if the contact layer is sufficiently thick to enable the mortar or adhesive to mesh with and practically fill the dovetail-shaped grooves. The mortar or hardened adhesive filling the grooves inhibits the ability of such plastic sheet to stretch in the direction transverse to the webs when it is mounted.
The purpose of the present invention is to provide a plastic sheet which serves as an insulating lining for building surfaces. The plastic sheet has parallel, alternating, open, sectioning which is dovetail-shaped in cross section. This material can be used to create a moisture-impermeable super-structure, enabling substantial compensation of foundation- or facing-induced stresses. The choice of the bonding media to be used, such as adhesives or mortar, can be simplified by using this plastic sheet.